In 1953, Rappaport found that β-particles generated by the decay of isotope can form electron-hole pair in semiconductors, and this phenomenon is called β-Voltaic Effect. Before long, Elgin-Kidde firstly applied the β-Voltaic Effect in the electric energy supply area in the year of 1957 and successfully prepared the first isotope micro battery β-Voltaic Battery. From 1989, GaN, GaP, AlGaAs, polycrystalline silicon etc. were used one after the other as the material for β-Voltaic Battery. As the development of the preparation and process technology for wide band gap semiconductor material SiC, from 2006, there are relevant reports on the isotope micro battery based on SiC both in domestic and overseas.
Patent Document 1 discloses a Schottky junction nuclear battery based on SiC proposed by Lin Zhang, Hui Guo etc. As shown by FIG. 2, said Schottky junction nuclear battery from top to bottom, comprises a bonding layer 1, a Schottky contact layer 13, a SiO2 passivation layer 4, an n-type low-doping SiC epitaxial layer 5, an n-type high-doping SiC substrate 6, an ohmic contact electrode 7. In the Schottky junction nuclear battery, the Schottky contact layer covers the whole battery area, after the injecting particles reach the surface of the equipment, they will be blocked by the Schottky contact layer and only partial particles can enter into the inside of the equipment, and only the particles entering into the depletion area can have contribution to the output of the battery. Therefore, for the nuclear battery with such structure, the injecting particles lose a large number of energy and the energy conversion is low.
Non-patent Document 2 introduces a SiC p-i-n junction nuclear battery proposed by M.V.S. Chandrashekhar, C. I. Tomas, Hui Li, M. G Spencer and Amit Lal etc. from Cornell University in New York, US. As shown by FIG. 1, said p-i-n junction nuclear battery from top to bottom, comprises a radioactive isotope source layer 3, a p-type ohmic contact layer 12, a p-type high doping SiC layer 9, a p-type SiC layer 11, an intrinsic I layer 10, an n-type high doping SiC substrate 6, an ohmic contact electrode 7. In said structure, the substrate is p-type high doping substrate, and the technology of growing epitaxial layer thereon is not mature. So, surface defect is easy to be introduced, the leaking current of the device is increased, and the energy conversion rate is low. Meanwhile, a p-type low doping SiC layer is formed by unintentionally doping epitaxial growing, the doping concentration is high, the width of the resulting depletion area is small and the carrier generated cannot be completely collected, and thus the open circuit voltage of the device is low and the energy conversion rate is low.
In addition, it is known that doping ions such as vanadium, iron etc can be used to compensate the free carrier in SiC material, and a SiC material having semi-insulation property can be obtained. But, this technology has not been applied in the field of nuclear battery.